Antenna array excited by voltages of varying amplitude



Dec. 2, 1958 J. RUZE 2,863,146

' ANTENNA ARRAY EXCITED BY VOLTAGES 0F VARYING AMPLITUDE Filed March 9, 1953 4 Sheets-Sheet 1 DINVENTOR JOHN RUZE BYz ATTORNEYS Dec. 2, 1958 J. RUZE ANTENNA ARRAY EXCITED BY VOLTAGES OF VARYING AMPLITUDE Filed March 9, 1953 AMPLITUDE 0F yams! i/514mm? Z5170" ANTENNA APERTURE AMPLITUDE 0F VOLTAGE ANTENNA APERTURE Cflg'y 5 AMPLITUDE 0F VOLTAGE W ANTENNA APERTURE AMPLITUDE 0F VOLTAGE pisrmciiio'ivfi ANTENNA ,APERTURE 4 Sheets-Sheet 2 AMPLITUDE or SIGNAL AMPLITUDE 0F SIGNAL ANGLE a AMPLITUDE DF SIGNAL AMPLITUDE 0F SIGNAL INVENTOR. JOHN RUZE ATTORNEYS Dec. 2, J. RUZE' v ANTENNA ARRAY EXCITED BY VOLTAGES OF VARYING AMPLITUDE Filed March 9, 1953 4 Sheets-Sheet 3 I o v E b {a g 11e g 3 a 2 I o v 8 4 32 o 8 2a a: 1, 1:29-13 -13 +22 I I 4 l3 Z. l3 2 SW [2 1 1-2 18 v w 5 W12 a /I: 4 20 4: 4 10 INVENTOR. 7 5 J2 JOHN RUZE 14 I BY 6 w ATTORNEYS Dec. 2, 1958 v JQRUZE v 2,863,146

Filed March 9, 1955 4 Sheets-Sheet 4 AMPLITUDE 0F Admiral: or yarn:

DISTANCE MU ANTENNA PERTH:

I 152 r l l INVENTOR. JOHN RUZE BY 1mm ATTORNEY/S United States Patent 70 ANTENNA ARRAY EXCETED BY VOLTAGES 6F VARYING AMPLITUDE John Ruze, Cambridge, Mass, assignor to The Gabriel Company, Cleveland, Ohio, a corporation of Ohio Application March 9, 1953, Serial No. 341,231

22 Claims. (Cl. 343-770) The present invention relates to antennas and methods of operating the same and more particularly to antenna structures particularly adapted for use in the ultrahighfrequency range.

In some ultrahigh-frequency and very-high-frequency antenna transmitting systems, such as, for example, those employed for television transmissions, an omni-directional horizontal radiation pattern and a high-gain vertical radiation pattern are required to provide uniform broadcasting in all directions of azimuth and over a desired field of coverage. It is often the requirement, moreover, that the polarization of the radiated energy be horizontal. Many antennas have been designed for producing such patterns. Some of these antennas are in the form of helical arrays; others in the form of circular loops; still others employ antennas of various other configurations such as bat wings and the like; and antennas have also been proposed embodying a plurality of angularly disposed wave guides or horns, including bi-conical horns. Antennas of this character, however, are quite costly to manufacture, requiring specially designed components. Present-day commercial antennas of this type, moreover, utilize large numbers of cumbersome and expensive insulators which are subject to periodic deterioration under the influence of atmospheric conditions, and they require, also, phaseand impedance-correcting networks and other devices associated with the feed transmission lines that add cost and complexity to the equipment. Not only is it desirable to reduce the cost of manufacture of such antennas, therefore, but it is quite advantageous to eliminate the necessity for the use of insulators and such phase and impedance-correcting devices.

A very satisfactory antenna that obviates these difficulties is described in a copending application of Howard J. Rowland, Serial No. 251,516, filed October 16, 1951, now Patent No. 2,778,014. There are some instances, however, where in addition to overcoming these difficulties, either an extremely tall antenna structure is required, or a very high degree of circularity in the horizontal radiation pattern is essential, or both.

An object of the present invention is to provide a new and improved antenna of this character that is adapted to produce a very high degree of circularity in a horizontally polarized omni-directional radiation pattern in the horizontal plane, and that is constructionally adapted to support itself even when of very tall dimensions.

A further object of the invention is to provide such an antenna that is particularly adapted for use in the ultrahigh-frequency range.

The radiation pattern of an antenna inherently embodies nulls or radiation blind spots in which no energy can be radiated or received. In the case of transmitting antennas located upon towers displaced from the ground, nulls or radiation blind-spots are usually produced in the vertical-plane coverage of the transmitted energy. It has been proposed to try to overcome the disadvantages of such nulls by tilting the antenna. Though tilting the antenna will result in tilting the vertical-plane radiation pat- A 2,863,146 Patented Dec. 2, 1958 tern or beam, and thus may assist in directing the main or principal lobe thereof to cover an otherwise blind spot, it can not eliminate the nulls between the secondary lobes of the radiation pattern.

Another proposal, therefore, has been to supplement the antenna with a centrally or otherwise disposed supplemental non-directional antenna to produce some radiation in the regions of the nulls of the main antenna. Not only does this proposal require additional feed lines and phase-shifting networks for the supplemental antenna, but there is a loss of energy created that would have been available had this supplemental antenna been excited along with and in similar fashion to the main antenna.

In the microwave region, this problem has been somewhat overcome by shaping the antennas and reflectors so as to produce vertical radiation patterns that substantially follow a so-called cosecant-squared law. At television V. H. F. or U. H. F. frequencies, however, to space the antennas non-uniformly and to arrange complicated feeding devices in order to effect such a co-secant-squared pattern would be expensive and impractical.

An additional object of the present invention, therefore, is to provide an antenna and a method of operating the same that will overcome the effects of blind spots or nulls in the vertical radiation coverage without the abovedescribed disadvantages. Briefly, this is accomplished by varying the amplitude of the voltage fed to successive sets of the antenna elements of a vertical antenna array in successive steps of increasing amplitude.

()ther and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

From a more specific view point the invention relates, also, to a preferred antenna system for transmitting radiofrequency energy of a predetermined wavelength comprising a plurality of, preferably five, substantially parallel transmission-line conductors four of which preferably comprise tubular columns of substantially circular cross section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmissionline conductors. Means is provided, preferably in the form of a coaxial line, for energizing the fifth transmissionline conductor from the inner coaxial-line conductor and the tubular column transmission-line conductors in antiphase therewith from the outer coaxial-line conductor. Several branch-conductor groups each comprising four appropriately dimensioned branch conductors are disposed in substantially parallel planes norm-a1 to the transmission-line conductors and spaced therealong at intervals corresponding substantially to the said predetermined wavelength. The four branch conductors of each group are connected at one of their ends to the fifth transmissionline conductor and at their other ends to substantially co-planar points disposed in the outer surfaces of the respective four tubular column transmission-line conductors to radiate horizontally polarized waves omni-directionally with a high degree of circularity in the horizontal pattern. Means is provided for varying the amplitude of the voltage fed to the tubular columns at successive branch-conductor groups in successive steps of increased amplitude, thereby filling the undesirable vertical radiation-pattern blind spots or nulls. Preferred constructional details and dimensions will be hereinafter pointed out.

The invention will now be described in connection with the accompanying drawings Figs. 1 and 2 of which are schematic diagrams representing vertical radiation pattern distributions produced by antennas elevated above the ground;

Figs. 3, 5, 7 and 9 are graphs representing various types of voltage distributions along an antenna;

Figs. 4, 6, 8 and 10 are graphs representing the lobe radiation patterns produced by antennas fed in accordance with the respective voltage distributions of Figs. 3, 5, 7 and 9;

Fig. 11 is a perspective view of a preferred form of the invention, partly cut away to illustrate structural details;

Figs. 12, 13, 14, 15 and 16 are sectional views taken upon the respective lines 1212, 1313, 14-14, 1515 and 1616 of Fig. 11, looking in the direction of the arrows;

Fig. 17 is a perspective of a further modification;

Fig. 18 is a graph explanatory of the voltage distribution along the antenna of Fig. 17; and

Fig. 19 is a graph representing the radiation pattern produced by the antenna of Fig. 17.

In Fig. 1, an antenna comprising a vertical array or plurality of radiating elements is generally indicated at 1, positioned upon a tower 9 above the surface of the ground 25. The term ground is herein used in the generic sense to represent any portion of the earths surface including bare earth, cities, bodies of water and the like. The antenna may comprise a plurality of spaced vertical columns, later discussed in connection with the preferred embodiment of Fig. 11, of which the columns 4 and 6 are illustrated. If the antenna 1 assumes the form of Fig. 11, then it will radiate in all directions in the horizontal plane, as later described. A vertical section only of the radiation pattern in the direction from le-ft-to-right, is shown in the drawing. This vertical radiation pattern or beam comprises a main or principal lobe E represented by the successive electric-vector or field-strength contour lines E E E E E E E etc. Considering the radiation in the horizontal direction, the intensity that may be received from the point at the center of the antenna 1 is of value E at the limit of the first contour lobe E of lesser value E at the limit of the second contour lobe E and so on, being of much smaller value E at the limit of the contour lobe E At any angle 0 from the horizontal and at any arbitrary distance OP from the antenna, for example, a value of field strength will be received that is greater than E but not so great as E All of the contours E E E E E E E etc. are intended to describe successive portions of the main or principal radiation lobe of the vertical pattern. It will be observed that the right-hand portion of the city 27 receives radiation from the E contour of this main lobe E.

As before stated, the antenna 1 has inherent blind spots, openings, gaps or nulls in its radiation pattern, as shown, for example, in the shaded areas 29 and 31. Between these null areas 29 and 31, however, smaller amounts of energy are radiated in a first secondary lobe, S. the contour lines of which are shown at S S S S S S S etc. Between the secondary lobes S to S etc. and the main lobe E to E etc. is the opening, gap or null defined by the lines bounding the area 29. The left-hand edge of the city 27 will be provided with radiaation by this first secondary lobe Si to S etc., with a field strength indicated by the contour line S Similarly, a second secondary lobe, T, represented by the contours T T T T T T etc. is shown to the left of the blind area 31. There are in practice, many more than two nulls and many more than two secondary lobes, though the above example fully illustrates the points involved. The symmetrical secondary lobes above the principal lobe E need not be considered since they effect upward radiation.

In accordance with the present invention, the underside portions of the contours E to E etc. of the main or principal lobe, instead of being separated by an opening or gap from the secondary lobe S to S etc. as in Fig. 1, are merged with upper portions of the contours of the first secondary lobes S to S etc. as illustrated at M M M M M M etc. This merging serves partially to fill the gap or opening shown in Fig. 1, providing radiation in the regions M to M etc. where previously the blind area 29 had existed. Radiation will thus be spread over the complete city 27 without a blind area. Similarly the blind-area opening, gap or null region 31 is partially filled in by the merging of the first secondary lobe contours S to 8 etc. with the respective second secondary lobe contours T to T etc. at N to N6, etc.

In actual practice, the most important null or gap to fill in is that represented by the shaded area 29, between the main lobe E and the first secondary lobe S. If regions closer to the transmitting antenna 1 must be voided of blind areas, then the gaps between the various successive secondary lobes may also be filled in. The technique for effecting this result will now be explained in terms of any type of antenna, though a preferred antenna system will later be described.

Another Way of graphically illustrating the performance illustrated in Fig. 1 is set forth in Figs. 3 and 4. In Fig. 3 the ordinate represents the amplitude of the radio-frequency voltage fed to the antenna 1. Successive points along the abscissa represent successive points upward along the antenna 1. With uniform amplitude of voltage fed to all the antennas along the vertical array 1, as represented by the fiat curve 33, a radiation pattern will be produced of the character represented by the polar lobe contours E, S, T of Fig. 1. Instead of using polar coordinates, however, a Cartesian plot may be made, as in Fig. 4, where the ordinate represents the amplitude or field strength of the radiated signal and the abscissa represents the angle 0 of deviation from the horizontal line emanating from the point 0 in Fig. 1. The principal lobe E of Fig. 1 is shown vertically oriented in Fig. 4. The first secondary lobe is shown at S; the second secondary lobe, at T; and still a third secondary lobe, not shown in Fig. l, at V. The symmetrical lobes to the left of the ordinate in Fig. 4 correspond to the lobes above the horizontal line 0 of Fig. 1. It is frequently convenient to draw this graph with the secondary lobes S and V positioned above the abscissa, as shown dotted at S and V. The nulls 29 and 31 are also evident in Fig. 4 since zero signal amplitude is there indicated.

If, instead of energizing the antennas of the vertical antenna array 1 with the uniform voltage-amplitude distribution 33 of Fig. 3, however, successive antennas from the bottom to the top of the array were energized with voltage amplitudes of successively increasing value, as shown at 35 in Fig. 5, a different radiation pattern will be produced having a null or gap along the line 0, Fig. 6, and a principal lobe A to the right thereof, followed by a first secondary lobe B, that may also be represented by the dotted lobe B and a second secondary lobe C. While the radiation pattern of Fig. 4 produced a maximum amplitude of signal along the line 0, the pattern of Fig. 6 produces no signal. In the region corresponding to the null 29 between the principal lobe E and the secondary lobe S of Fig. 4-, it will be observed that the lobe A of the pattern of Fig. 6 is providing radiation. Similarly the lobe B of Fig. 6 provides radiation in a region corresponding to the null 31 of Fig. 4. The reason for this maximum-minimum correspondence between Figs. 4 and 6 may be evident when it is considered that the formula describing the pattern of Fig. 6 is the calculus derivative of the formula describing the pattern of Fig. 4. It may be shown, furthermore, that the patterns of Figs. 4 and 6 are in phase quadrature.

By combining the pattern ES'-TV' of Fig. 4 with the pattern AB--C of Fig. 6, therefore, the beforedescribed merging or partial filling of the nulls 29, 31, etc. may be effected, as at M, N, Q, etc., Fig. 8. This resultant pattern is obtained by combining the amplitude distributions of Figs. 3 and 5, thereby to feed the radiofrequency voltage in accordance with the successively increasing trapezoidal amplitude distribution 37 of Fig. 7,

the amplitude of the voltage increasing from the bottom to the top of the antenna array 1. The resultant pattern 39 of Fig. 8 corresponds to the merging contour pattern of Fig. 2. While it has before been proposed to taperfeed antenna arrays, as for merely reducing the size of secondary lobes or for varying the radiation distribution along a surface reflector, the present invention utilizes this particular tapered or substantially trapezoidal feed distribution in connection with the vertical antenna 1 disposed above the ground to achieve these novel nullfilling results.

In actual practice, an approximation to the trapezoidal amplitude distribution 37 is achieved by feeding successive sets of antennas with successively increased steps of voltage amplitude I, 11, Ill and IV, Fig. 9. A resultant pattern :1, Fig. 10, is produced corresponding closely to the pattern 39 of Fig. 8.

It is essential that the required amplitude distribution be effected while feeding the successive antennas of the array 1 with constant phase. The above description has proceeded upon this assumption of a substantially con stant phase distribution. There are several ways of achieving such superposition of the constant amplitude feed distribution 33, Fig. 3, and the successively increasing amplitude distribution 35, Pig. 5, of which two of the more important will hereinafter be described in connection with a preferred antenna, though it is to be understood that these techniques may equally well be applied to other types of antennas, as well. It is first desirable, therefore, to explain the details of the preferred type of antenna.

Among the commercially available self-supporting structures mass-produced for other fields of endeavor, such as building construction, are angle beams, rods and tubular columns of circular cross section, as of steel. In accordance with the present invention, four such similar devices are utilized as an antenna structure, the preferred devices being tubular columns. In Fig. 11, vertically arranged spaced tubular columns are shown at 2, 4, 6

and 8 symmetrically disposed with respect to a preferably substantially parallel centrally disposed transmission-line conductor it; and with substantially equal spacing S, Fig. 13, between the adjacent tubular columns. The centers of the columns thus form a square. The tubular columns are connected together at the bottom of the antenna by an end plate 7, as by welding or with the aid of bolts. The tops of the columns 2;, 4, 6 and 3 may be electrically connected by spacer plates 21 that aid in the mechanical support. A platform 57 may be welded or otherwise secured to the top of the antenna for supporting a beacon light It, the power cables of which, not shown, may be carried upward through one of the tubular columns, such as the column 4. The bottom end plate 7 is provided with an insulation-filled aperture 5 for receiving the centrally disposed transmission-line conductor and its terminal connector it), and may be secured to the top of a conventional antenna tower 9, as by welding or any other desired means. As wiil hereinafter appear, the structural properties of the tubular columns and the associated energizing conductors are such that no bracing or other auxiliary supporting devices are required even if very tall structures are utilized.

The tubular columns 2, l, 6 and S are all connected by the plate 7 to the outer conductor 12 of a coaxialfeed transmission line to serve as equipotential transmission-line conductors energized thereby. The transmission-line conductor iii is energized in anti-phase therewith through its connection by the terminal connector 10 with the inner conductor ltd of the coaxial-feed transmission line that, in turn, connects with, for example, a television transmitter, not shown, located, perhaps, at the base of the tower 9. The antenna structure may be grounded through the tower 9.

Along the transmission-line conductors 2, 4, 6, 8 and 10, several sets of branch-conductor groups are providascents ed each comprising four branch conductors, such as 18, 24, 32 and 34, disposed in substantially parallel planes preferably substantially normal to the transmission-line conductors and spaced therealong vertically at intervals corresponding substantially to the predetermined wavelength with which the antenna is to operate.

The branch conductors 18, 24, 32 and 34 are connected atone of their ends to the centrally disposed transmission-line conductor 10, as at 13, extend, in part, radially outward and then preferably extend at right angles as shown at 22. At their other ends, the branch conductors are connected to preferably co-planar points along the outside surfaces of the respective tubular column transmission-line conductors 6, 8, 2 and 3 by the preferably horizontally disposed connecting portions 22, as at points 29. Each branch conductor, such as, for example, the branch conductor 18, becomes one element of a further three-element branch transmission line the other two elements of which comprise the side of the tubular column conductor to which it is connected, such as the righthand side of the tubular column conductor 6, and the side of the adjacent tubular column conductor, such as the left-hand side of the tubular column conductor 4. Current then flows outward along the branch conductor 18 and back in the opposite direction along the righthand side of the tubular column conductor 6, but in the same direction along the left-hand side of the tubular column conductor as along the conductor 18. The appropriate impedance adjustment for this unbalanced three-conductor feed may be eifected by adjusting the position of the point 26 along the right-hand side of the tubular column conductor 6. For the purposes hereindescribed, it has been found advantageous to locate the point 29 right near the outer edge of the tubular column conductor, as shown. If desired, a stub, not shown, may be used at the top of the array for assisting in matching the complete array. The location of the points 20 along one of the side edges of each tubular column may also be adjusted to effect desired phase relationships. The spacing S between the parallel sides of the adjacent columns and the spacing from the inner conductor 10 may also be varied to effect desired impedance and phase relationships without the necessity for utilizing special lines, networks or other devices.

With such an arrangement, moreover, the rectangular wave-transmission loops or frames formed by the outer rims or edges of the transmission lines 2, 4, 6, 8 and the spacers 21, are provided with long sides such as 4, 6, about a wavelength in length, shorter sides 21 less than a half-wavelength in length, and since only essentially the outer rims or edges are effective, an effective depth or thickness of negligible dimensions. The feed system embodying the exciters, 18, 2d, 32, 34, moreover, with the end portions 22 substantially in the plane of the loop or frame, may be oriented substantially parallel to the shorter sides, formed by the spacers 21, and thus insuring excitation by radio-frequency energy of polarization perpendicular to the plane of the longer sides 4, 6 of the frame.

While the length of the branch conductors 18, 24, 32 and 34 can be made small, consistent with preventing the short-circuiting of the energy that is passed upward along the five-conductor transmission lines 2, 4, 6, 8, 10, and outward to the outer edges of the tubular column conductors 2, 4, 6 and 8, it can not be made too large without producing sharp lobes in the radiation pattern of the antenna that destroy the circularity of the desired omni-directional radiation pattern. The overall width or diameter of the antenna array, on the other hand, must be large enough to support the necessary structure. If the degree of circularity or omni-directionality of the horizontal field pattern produced by the antenna, defined in terms of the maximum-to-minimum field intensity ratio in the pattern, is to be very great, the length of the branch conductors 18, 24, 32 and 34 should be substantially equal to or less than about the half-wavelength of the radio energy. The spacing S between the parallel side surfaces of the adjacent beam conductors 2, 4, 6 and 8, furthermore, is preferably adjusted to a value considerably less than the length of the branch conductors in order to maintain the omni-directional radiation pattern characteristic. An antenna particularly suited for the ultra-high-frequency range of from about 500 to about 890 megacycles per second, for example, having branch conductors 18, 24, 32, 34 of length about four and onehalf inches, tubular columns of diameter about four inches and a spacing S between the parallel sides of adjacent angular beams of about one inch, has been found to produce a remarkable degree of circularity in the omni-directional horizontal pattern. For antennas designed for operation with different predetermined wavelengths in the said 500 to 890 megacycle range, the length of the branch conductors may vary from about three and one-half to about six inches; the diameter of the tubular column conductors, from about three to about six inches; and the spacing S, from about one-half inch to about two inches.

, It has been found that the circularity of the omnidirectional pattern is markedly improved over that obtainable with other types of structural conductors since circular auxiliary current paths form transversely along the circular sides of the tubular column transmission-line conductors along their complete length. This construction also appears to minimize cross-polarization effects since any vertically polarized radiation components that may be set up are interrupted by the horizontal path for current provided by the circular contour around the outer surfaces of the tubular columns.

As an illustration of the unusual effectiveness of the tubular column outer surface circular contour, the before-described antenna was operated at a frequency of about 800 megacycles with maximum variations of less than 0.5 decibel from the mean value in the horizontal pattern.

An array of this character, about ten to twenty wavelengths long, Will. produce suflicient directivity and gain in the vertical plane for the television purposes before mentioned. A twelve-wavelength array, for example, has been found to produce a half-power vertical principal lobe angle of about 4.2 degrees. A high gain of 11 decibels over a tuned dipole was achieved, with a power gain of 14 and a voltage standing-wave ratio of less than 1.1 to 1.

Not only does the use of the tubular columns and the associated transmission-line system completely obviate the necessity for bracing or other auxiliary supports, as before pointed out, even for great heights, but the necessity for insulators has also become obviated. Except for providing additional structural rigidity, moreover, the spacer elements 21, disposed at each wavelength interval along the array, need not be employed insofar as electrical performance is concerned. Bolts or other securing means, if any, may, indeed, be substituted therefor.

This type of antenna may, of course, be utilized for other purposes than providing the best possible omnidirectional pattern, in which event symmetry may not be required and less than or more than four angular beams may be utilized. The branch conductors 18, 24, etc. may then extend in other directions than at right angles to the axis of the conductor 10. Tho-ugh the antenna structure of the present invention has been discussed in connection with its application to ultra-high-frequency transmissions, such as in the television field. furthermore, it will be understood that the antenna may, if desired, be adapted for use, also, as a receiving structure in which event the before-mentioned transmitter will be replaced by a receiver. The antenna may, also, by appropriate scaling of its dimensions, be applied to frequencies in the ,very-high-frequency range as well as to frequencies above the ultrahigh-frequency range. It is not essential, moreover, though it is most convenient, to utilize the coaxial type of transmission-line feed, for other types of feed lines may be employed.

While the before-described arrangement of the preferred embodiment of Fig. 11 is particularly adapted for television purposes, furthermore, tubular column structuresof elliptical, square, rectangular or other configuration may be utilized as the structural element, though the circular cross section has been found to produce the previously described extremely high degree of circularity in the horizontal pattern.

Plexiglas, polyvinyl chloride or similar radio-wave transparent sheet material, such as the flat strips 52, Fig. 11, may be inserted within guides 152 and secured, as by screws 3 or other means, to the edges of the spacers 21, to close off the space between the parallel sidesof the adjacent angular beam transmission-line conductors to the effects of the atmosphere.

The step-feed distribution I, II, III, IV of Fig. 9 may be achieved with this antenna by utilizing branch conductors, in successive sets of antenna-radiating portions or elements of the array 1, the impedance of which successivelydecreases. Thus the branch-conductor groups 18, 24, 32, 34 feeding the bottom two-wavelength antenna radiating portions or elements are of a small diameter. Figs. 11 and l3;'the branch-conductor groups 118, 124, 132, 134 of the next higher set of two antenna elements are of a larger diameter, Figs. 11 and 14; the branchconductor groups 218, 224, 232, 234 of the next higher set of antennas are of still greater diameter; and the branch-conductor groups 318, 324, 332, 334 of the uppermost set of antennas of the array 1, Figs; 11 and 16, are of still greater diameter. Thus, successively increased amplitude of voltage is fed to the successive sets of antenna elements as shown at I, II, III and IV, Fig. 9, producing the resultant patern 41 of Fig. 10.

The above example of two antenna elements for each set of antennas, in the array 1 is only for illustrative purposes, more or less elements being utilizable. It has been found that with a 12-wavelength 12-element array of the character illustrated in Fig. 11, having the four-step substantially trapezoidal feed, that the first three nulls of the vertical radiation pattern are successfully gap-filled.

In Fig. 17, as another example, only a two-step amplitude distribution is utilized. The upper array B is fed with a greater amplitude of voltage than the lower array A, though all the antenna elements are fed in constant phase. The voltage distribution along the complete array A-B is thus shown at III in Fig. 18. This twostep distribution could have been achieved in the manner discussed in connection with Fig. 11. It is shown as achieved, however, in a different manner, which could also have been applied to the antenna of Fig. 11 if the use of a separate feed system were unobjectionable. In Fig. 17, the inner conductor 10 of the lower section A is connected to the base plate 7. The outer conductor 12 of the coaxial feed system 1214 is also connected to the base plate 7, and the inner conductor 14 is extended, as at 114, upward within the tubular column 4. At the midway junction between the antenna sections A and B, formed by the sandwich-type supporting-plate conductive connectors 59-63, the inner conductor extension 114 branches right-angularly, as at 16, and connects at 209 with the bottom of the central conductor 10' of the upper array B and the top of the central conductor 10 of the lower array A. Appropriate power division to achieve the two-step amplitude feed III of Fig. 18 is effected with the aid of different impedance transformers 109 and 106 interposed between the connection 209 and the central conductors 10 and 10' of the lower and upper arrays A and B, respectively. Proper phasing may be achieved through the movement of the capacitive plunger 121 in the stub section 123 formed by the portion of the branch 16 to the right of the conductor 114 and the outer sleeve 104 connected with and branching from the. tubu- 9 lar conductor 4. The beacon-light power cable 120 may be carried upward to the light 11 through the tubular conductor 6.

It has been found that the two-step feed of Figs. 17 and 18 will tend to fill the nulls or gaps between every other pair of lobes instead of between successive pairs of lobes, as in Fig. 10. Thus in Fig. 19, the resultant pattern 141 of the system of Fig. 17 is plotted, showing filling in the region M between the principal lobe E and the first secondary lobe S, no filling between the first secondary lobe S and the second secondary lobe T, but filling at Q between the second secondary lobe T and the third secondary lobe V, and so on. Where only the first null is to be filled or where the gap between the first and second secondary lobes is not objectionable, this system is quite satisfactory. Further modifications will occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A vertically oriented substantially co-planar array of antennas disposed above the ground having means for exciting the antennas with the same radio-frequency voltage and means for varying the amplitude of the voltage in successively increasing steps along successive sets of the antennas of the array, from the bottom thereof to the top.

2. A vertically oriented substantially co-planar array of antennas disposed above the ground having means for exciting the antennas with the same radio-frequency voltage and means for varying the amplitude of the voltage applied to successive sets of the antennas of the array, from the bottom thereof to the top, in accordance with a substantially trapezoidal distribution of successively increasing amplitude.

3. An antenna comprising four similar right-singularly disposed vertically oriented horizontally polarized antenna arrays placed the same height above the ground, means for similarly exciting the four antenna arrays simultaneously with the same radio-frequency voltage, and means for simultaneously varying the amplitude of the voltage in similar successively increasing steps along similar successive sets of the antennas of each array, from the bottom thereof to the top.

4. An antenna comprising four similar right-angularly disposed vertically oriented horizontally polarized antenna arrays placed the same height above the ground, means for similarly exciting the four antenna arrays simuitane ously with the same radio-frequency voltage, and means comprising feed lines of successively decreasing impedance for simultaneously varying the amplitude of the voltage in similar successively increasing steps along similar successive sets of the antennas of each array, from the bottom thereof to the top.

5. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radiofrequency energy of the said predetermined wavelength and the said other transmission-line conductors in antiphase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmissionline conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmission-line conductors and each of length not greater than approximately one-half the said prei 10 determined wavelength, and means for feeding difierent amplitudes of the radio-frequency energy to the said other transmission-line conductors at difierent branchconductor groups.

6. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in antiphase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmissionline conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmission-line conductors and each of length not greater than approximately one-half the said predetermined wavelength, and means for feeding successively greater amplitudes of the radio-frequency energy to the said other transmission-line conductors at successively disposed branch conductor groups.

7. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equai in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmissionline conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmission-line conductors and each of length not greater than approximately one-half the said predetermined wavelength, and means for feeding successively greater amplitudes of the radio-frequency energy to the said other transmissio-n-line conductors at successive sets of successively disposed branch-conductor groups.

8. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plu rality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmissiondine conductors, means for energiring the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmissiondine conductors in anti-phase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equal in num' her to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conduct-or and at their other ends to points disposed along the outer surfaces of the respective other transmission-line conductors and each of length not greater than approximately one-half the said predetermined wavelength, and

'11 means for feeding a greater amplitude of the radio-frequency energy to the said other transmission-line conductors at one set of successively disposed branch-conductor groups than at a second set of successively disposed branch conductor groups.

9. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmissionline conductors and each of length not greater than approximately one-half the said predetermined wavelength, and means for feeding successively greater amplitudes of the radio-frequency energy to the said other transmissionline conductors at four successive sets of successively disposed branch-conductor groups,

10. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmis- Sion-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equal in numher to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmissionline conductors and each of length not greater than a-pproximately one-half the said predetermined wavelength, and means for feeding the radio-frequency energy to the said other transmission-line conductors at successive sets of successively dis-posed branch-conductor groups in successive steps of increased amplitude.

11. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmis si-on-line conductors of length several times the said predetermined wavelength, one of the transmission-line conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, a plurality of branch-conductor group each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmissionline conductors and eachof length not greater than approximately one-half the said predetermined wavelength; and means for feeding the radio-frequency energy to the said other transmission-line conductors at successive sets of successively disposed branch-conductor groups with an amplitude distribution of substantially trapezoidal shape.

12. An antenna system for transmitting radio frequency energy of a predetermined wave-length comprising a plurality in excess of two of substantially parallel transmis sio-nline conductors of length several times the said predetermined wavelength, all but one of the transmissionline conductors comprising tubular columns symmetrically disposed with respect to the other transmission-line conductors, means for energizing the said one transmissionline conductor with radio-frequency energy of the said predetermined wavelength and the said other transmissionline conductors in anti-phase therewith, a plurality of branch-conductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective tubular column transmission-line conductors and each of length not greater than approximately one-half the said predetermined wavelength, and means for feeding different amplitudes of the radiofrequency energy to the said other transmission-line conductors at diiferent branch-conductor groups.

13. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmissionline conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, a plurality of branchconduc tor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmission-line conductors and each of length not greater than approximately one-half the said predetermined wavelength, the impedance of different branch-conductor groups being difierent to feed correspondingly different amplitudes of the radio-frequency energy to the said other transmission-line conductors at the different branch-conductor groups.

14. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, one of the transmissionline conductors being disposed symmetrically with respect to the other transmission-line conductors, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, a plurality of branch-com ductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being disposed within the space between the transmission-line conductors and the branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective other transmission-line conductors and each of length not greater than approximately one-half the said predetermined wavelength, the thickness of the branch conductors of the different branch-conductor groups being different to feed correspondingly different amplitudes of the radio-frequency energy to the said other transmission-line conductors at the different branch-conductor groups.

15. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length several times the said predetermined wavelength, all but one of'the transmission-line conductors comprising tubular columns symmetrically disposed with respect to the said one transmission-line conductor, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in antiphase therewith, and several branch-conductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmissionline conductors, the branch-conductor groups being disposed within the space between the transmission'line conductors in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, the plurality of branch conductors of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to substantially co-planar points disposed along the outer surfaces of the respective tubular column transmission-line conductors and each of length not greater than approximately one-half the said predetermined wave length and means for feeding different amplitudes of the radio-frequency energy fed to the tubular columns at different branch conductor groups.

16. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors of length at least equal to several times a predetermined radio-frequency wavelength, four of the transmission-line conductors comprising tubular columns of substantially circular cross-section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmission-line conductors, means for energizing the fifth transmission-line conductor with radio-frequency energy of the said predetermined Wavelength and the tubular column transmission-line conductors in anti-phase therewith, and several branch-conductor groups each comprising four branch conductors, the branch-conductor groups being disposed in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, conductive supporting plates connected between adjacent tubular column transmission line conductors substantially mid-way between successive groups of branch conductors, the four branch conductors of each group being connected at one of their ends to the fifth transmission-line conductor, extending radially between the adjacent tubular column transmission-line conductors, extending near their other ends at right angles to the said radial extensions and connected at their said other ends to substantially co-planar points disposed along the outer surfaces of the respective four tubular column transmission-line conductors near the outermost portions thereof and each of length not greater than approximately one-half the predetermined wavelength, and means for feeding different amplitudes of the radio-frequency energy to the tubular columns at different branch conductor groups.

17. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors of length at least equal to several times a predetermined radio-frequency wavelength, four of the transmission-line conductors comprising tubular columns of substantially circular cross-section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmission-line conductors, means for energizing the fifth transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in anti-phase therewith, and several branch-conductor groups each compris, ing four branch conductors, the branch-conductor groups being disposed in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, conductive supporting plates connected between adjacent tubular column transmission-line conductors substantially mid-way between successive groups of branch conductors, the four branch conductors of each group being connected at one of their ends to the fifth transmission-line conductor, extend ing radially between the adjacent tubular column transmission-line conductors, extending near their other ends at right angles to the said radial extensions and connected at their said other ends to substantially co-planar points disposed along the outer surfaces of the respective four tubular column transmission-line conductors near the outermost portions thereof and each of length not greater than approximately one-half the predetermined wavelength, the impedance of different branch-conductor groups being different to feed correspondingly different amplitudes of the radio-frequency energy to the said other transmission-line conductors at the different branch-com ductor groups.

18. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors of length at least equal to several times a predetermined radio-frequency wavelength disposed vertically above the ground, four of the transmission-line conductors comprising tubular columns of substantially circular crosssection symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmission-line conductors, means for energizing the fifth transmissiorr line conductor with radio-frequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in anti-phase therewith, and several branch-conductor groups each comprising four branch conductors, the branch-conductor groups being disposed in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, conductive supporting plates con nected between adjacent tubular column transmission-line conductors substantially midway between successive groups of branch conductors, the four branch conductors of each group being connected at one of their ends to the fifth transmissiondine conductor, extending radially between the adjacent tubular column transmission-line conductors, extending near their other ends at right angles to the said radial extensions and connected at their said other ends to substantially coplanar points disposed along the outer surfaces of the respective four tubular column transmission-line conductors near the outermost portions thereof and each of length not greater than approximately onehalf the predetermined wavelength, and means for feeding the radio-frequency energy to the said other transmission-line conductors at successive sets of successively disposed branch conductor groups in successive steps of increased amplitude.

19. Apparatus for partially filling in the gap between the principal radiation lobe and the first secondary radia- .tion lobe of the vertical radiation pattern of a substantially co-planar vertical array of antennas disposed above the ground that comprises means for substantially uniformly exciting the antennas of a lower portion of the array with a radio-frequency voltage of a predetermined amplitude and means for simultaneously uniformly exciting the antennas of an upper portion of the array with an identical radio-frequency voltage of greater amplitude.

20. Apparatus for partially filling in the gaps between the principal radiation lobe and the first secondary radiation lobe and between two or more of the secondary radiation lobes of the vertical radiation pattern of a substantially co-planar vertical array of antennas disposed above the ground that comprises means for exciting the array of antennas with a radio-frequency voltage, and means for varying the amplitude of the voltage in successively increasing steps along successive sets of the antennas of the array, from the bottom thereof to the top.

21. Apparatus for partially filling in the gaps between the principal radiation lobe and the first secondary radiation lobe and between two or more of the secondary radiation lobes of the vertical radiation pattern of a substantially co-planar vertical array of antennas disposed above the ground that comprises means for exciting the array of antennas with a radio-frequency voltage, and means for varying the amplitude of the voltage applied to successive 16 sets of the antennas of the array, from the bottom thereof to the top, in accordance With a substantially trapezoidal distribution of successively increasing amplitude.

22. Apparatus for partially filling in the gaps between the principal radiation lobe and the first secondary radiation lobe and between two or more of the secondary radiation lobes of a vertical radiation pattern, substantially omni-directional in the horizontal plane, of four rightangularly disposed vertical arrays of horizontally polarized antennas placed the same height above the ground that comprises, means for similarly exciting the four arrays of antennas simultaneously with a radio-frequency voltage, and means for simultaneously varying the amplitude of the voltage in similar successively increasing steps along similar successive sets of the antennas of each array, from the bottom thereof to the top.

References Cited in the file of this patent UNITED STATES PATENTS 2,149,415 Berndt Mar. 7, 1939 2,425,887 Lindenblad Aug. 19, 1947 2,429,629 Kandoian Oct. 28, 1947 2,496,242 Bradley Jan. 31, 1950 2,521,550 Smith Sept. 5, 1950 2,611,867 Alford Sept. 23, 1952 2,665,382 Smith Jan. 5, 1954 

